1. Field of the Invention
The present invention generally relates to medical catheters which are used for the irradiation of biological tissues, such as devices for the ablation of biological tissues, and more particularly to such a device incorporating a tracking sensor.
2. Related Art
Catheters are used for a number of procedures, including diagnostic, therapeutic, and ablative procedures. In such procedures, a catheter is moved through a patient's body to a desired treatment site. Therapeutic issue ablation systems apply energy to a biological ablation tissue site via different energy exchange means, such as heat conduction and irradiation. These systems may employ various energy modes, such as radiofrequency, ultrasound, laser, cryogenic, and the like. Within the radio frequency (RF) range, certain microwave ablation systems are used to destroy or ablate biological tissues. In one application, a microwave ablation system is used to ablate cardiac tissues that cause irregular heartbeats or arrhythmia, avoiding the need for more risky and invasive open heart surgery. In such an application, an ablation member such as an RF antenna is incorporated as part of a catheter. The catheter is passed through the vein for access to the atrium. Within the atrium, the RF antenna is positioned at the desired location where ablation is applied. Microwave ablation systems can also be used in treatment of other biological sites such as arteries, organs and body vessels. As an example, a microwave ablation system may be used to ablate tumors in the lungs, liver, kidney or other areas of the body.
These surgical and therapeutic applications require an efficient system for the transmission of radio frequency energy to the ablating member for the delivery of energy to the target tissue site. U.S. Patent Application Publication No. 20080015570 of Ormsby et al. describes a tissue ablation system comprising a hollow conductive coaxial cable having a first inner elongated electrically conductive tubular member having a distal end portion, the first tubular member having a hollow, axially extending lumen, a second elongated electrically conductive member disposed in a substantially coaxial relationship over at least a portion of the first electrically conductive tubular member over substantially the length of the cable, a dielectric medium disposed between the first and second electrically conductive tubular members, and an ablating member or radio-frequency antenna which delivers radio frequency energy including microwaves to body tissue disposed at the distal end portion of the cable. The radio-frequency antenna is adapted to receive and irradiate radio-frequency energy in the microwave range at a frequency typically greater than 300 Megahertz (MHz) in the electromagnetic spectrum for ablating biological tissue along a biological ablation pathway.
Radio frequency tissue ablation devices for surgical and therapeutic applications also require an accurate system for positioning the ablation device in the vicinity of the target tissue site. In typical procedures, X-ray fluoroscopy is used to locate the position of the distal end portion of the catheter and to display real time images of the site to medical personnel performing the procedure. Because these images are static and two dimensional, surgeons typically require many views to interpret the actual position in the body, and such positioning systems, taken alone, are subject to errors and incorrect interpretation. Such systems also expose the patient and medical personnel conducting the procedure to relatively high amounts of radiation.